Intravenous liposomal benznidazole as trypanocidal agent: increasing drug delivery to liver is not enough

With the aim of investigating if delivery of benznidazole (BNZ) to liver could be increased by incorporating the drug in multilamellar liposomes, single bolus of free BNZ or liposomal BNZ formulations (MLV-BNZ) composed of HSPC:DSPG:Chol 2:1:2 (mol/mol/mol) at 0.7% (w/w) drug/total lipid ratio, were injected by intramuscular (i.m.), subcutaneous (s.c.) and intravenous (i.v.) routes, at 0.2 mg BNZ/kg, in rats. The resulting blood concentrations were followed along 9 h post-injection (p.i.) and drug accumulation in liver was determined after 4 and 9 h p.i. Only upon i.v. injection of MLV-BNZ, a threefold higher BNZ accumulation in liver was obtained, together with blood BNZ concentrations of 1.1 microg/ml (30% lower than the blood BNZ concentration achieved upon i.v. administration of free drug) occurred 4 h p.i. However, such increased liver uptake of BNZ, raised twice a week had no effect on parasitaemia levels of mice infected with the RA strain of Trypanosoma cruzi. Our results indicate that the relationship between increased selectivity for an infected tissue and therapeutic effect is not always straightforward, at least for the MLV-BNZ regimen used in the present study.     

Bioavailability of a small unilamellar low-clearance liposomal amikacin formulation after extravascular administration

Amikacin in small, low-clearance liposomes (MiKasome) has prolonged plasma and tissue residence and in vivo activity against extracellular infections, including Klebsiella pneumonia and Pseudomonas endocarditis. Small liposomes may cross endothelial barriers, and enter the systemic circulation after extravascular administration. We compared the systemic bioavailability (F) of low-clearance liposomal amikacin in rats following intravenous (i.v.), intraperitoneal (i.p.), intramuscular (i.m.) and subcutaneous (s.c.) injection (20 mg/kg) and intratracheal (i.t.) instillation (10 mg/kg). Drug-containing liposomes were extensively absorbed after i.p. (F = 87-146%) and i.t. (F = 64%) administration, with maximum amikacin plasma concentrations of 171 micrograms/ml at 9 h and 80 micrograms/ml at 18 h, respectively. Absorption was slower and less extensive following s.c. (plasma Tmax: 20.3 micrograms/ml at 48 h) and i.m. (plasma Tmax: 49.6 micrograms/ml at 19 h) injection, but a significant fraction (12-27%) of the liposomes was absorbed. The plasma AUCs of liposomal amikacin exceeded the AUC of conventional i.v. amikacin by at least 25-fold for all routes. Amikacin AUCs in regional lymph nodes exceeded plasma AUCs by 4-fold after s.c. and i.m. injection of liposomal amikacin. AUCs in tissues surrounding the injection sites were 20- and 191-fold higher than plasma AUCs after i.m. and s.c. injection, respectively. Thus, small low-clearance liposomes produced sustained levels of liposome-encapsulated amikacin in plasma, local tissues and lymph nodes after extravascular administration, suggesting applications in perioperative prophylaxis, pneumonias and intralesional therapy as well as sustained systemic delivery of encapsulated drugs.     

Pharmacokinetics of phenobarbital and propylhexedrine after administration of barbexaclone in the mouse

The antiepileptic barbexaclone is the salt of the base propylhexedrine (indirect sympathomimetic) and phenylethylbituric acid. After i.v. and oral administration of 66 mg/kg barbexaclone to mice the time course of propylhexedrine and phenobarbital concentrations was studied in plasma, brain, lung, liver, kidney, spleen, heart, and skeletal muscle. Furthermore, the kinetics of phenobarbital were studied after treatment with an equimolar dose of phenobarbital-Na (40 mg/kg). In contrast to the i.v. bolus of phenobarbital-Na, barbexaclone was non-lethal only when infused over a period of 3 min. After the i.v. administration of either salt, phenobarbital plasma levels declined monoexponentially with a half-life of 7.5 h; the volume of distribution was 0.78 l/kg. After oral application absorption of phenobarbital was complete with both salts, though it was delayed after barbexaclone. The latter was the result of a delayed gastro-intestinal passage. Brain uptake of phenobarbital was a slow process, equilibrium with plasma concentrations being reached only 30 min after injection. Propylhexedrine reduced phenobarbital concentrations in brain as evident from steady state tissue-plasma ratios. This was observed after i.v. as well as after oral application. After i.v. application of barbexaclone the following pharmacokinetic parameters for propylhexedrine were determined: t0.5 alpha 0.31 h, t0.5 beta 2.5 h, Vd beta 19.3 l/kg; bioavailability (AUC oral/AUC i.v.) 0.37. Propylhexedrine penetrated the blood-brain barrier rapidly. High but unequal tissue accumulation was observed: lung = kidney greater than liver = brain greater than spleen greater than heart greater than skeletal muscle.     

Toxicokinetics and oral bioavailability of fumonisin B1

The kinetics of fumonisin B1 (FB1) after single doses of 10 mg FB1/kg (po) or 2 mg FB1/kg (i.v.) were studied in male Wistar rats. Serial blood samples were obtained after p.o and i.v. administration. Liver and kidney tissue samples were also obtained after p.o administration. Plasma, liver and kidney concentrations of FB1 were determined by a reversed-phase high-performance liquid chromatographic assay using precolumn 0-phthaldialdehyde derivatisation with fluorescence detection. The FB1 plasma profile could be adequately described by a 2-compartment open model. For FB1, the elimination half-life from plasma was 1.03 h after i.v. and 3.15 h after p.o administration. The apparent volume of distribution and volume of distribution at steady state for FB1 were 0.11 and 0.072 L, respectively, after i.v. administration. The total plasma clearance of FB1 was the same for both the p.o and i.v. routes, 0.072 L/h. After the single p.o dose, FB1 was rapidly absorbed with a Tmax of 1.02 h. The maximum plasma concentration of FB1 was 0.18 microgram/mL. The p.o bioavailability of FB1 was 3.5%. The tissue concentration time data for FB1 fit a 1-compartment open model. Considerable concentrations of FB1 were found in the liver and kidney tissues. The elimination half-lives for FB1 were longer for liver (4.07 h) and kidney (7.07 h) than for plasma (3.15 h). Tissue accumulation of FB1 was evidenced by the tissue/plasma area under the concentration-time curve (AUC) ratios; the AUCtissue/AUCplasma for FB1 was 2.03 in liver and 29.89 in kidney.     

Disposition of 3H-cholesteryl ether labeled liposomes following intravenous administration to mice: comparison with an encapsulated 14C-inulin as aqueous phase marker

In this study, the blood clearance and organ distribution of intravenously administered liposomes (distearoyl phosphatidylcholine [DSPC] and cholesterol in a ratio of 3:1) was evaluated by utilizing 3 H-cholesteryl ether as the lipid phase marker. Also, the ability of liposomes, as a drug delivery system, to alter the distribution and retention of encapsulated agents was investigated by comparing the distribution of intravenously administered free and liposome-encapsulated 14 C-inulin within a 48-hr postadministration period. Intravenously administered DSPC liposomes were distributed in all organs examined with the highest levels of 3 H-cholesteryl ether and 14 C-inulin present in the liver and spleen; peak levels occurred 3 hr postadministration (71.86% ±9.39 versus 77.67% ±10.30, respectively, in the liver and 5.05% ±1.07 versus 5.36% ±1.09, respectively, in the spleen) declining gradually during the remaining experimental period. The lowest levels of 3 H-cholesteryl ether and 14 C-inulin following administration of liposome-encapsulated inulin were found in the lung, kidney, and heart. The area under curve showed much more accumulation of 14 C-inulin (6-fold higher) in the body following administration of the liposome-encapsulated drug than the free drug. The ratio of 3 H to 14 C following administration of liposome-encapsulated inulin was constant throughout the entire observation period, suggesting that the disposition of inulin acquired both the carrier's rate of clearance and tissue distribution. These results indicated that following intravenous administration of liposome-encapsulated inulin, the majority of the radioactively labeled formulation was retained by the organs of the reticuloendothelial system (liver and spleen); liposomes greatly enhanced the retention of inulin in the body; and the liposomal formulation did not destabilize and subsequently did not release the encapsulated inulin to the tissues and organs.     

Pharmacokinetics of liposome-encapsulated anti-tumor drugs: Studies with vinblastine,actinomycin D,cytosine arabinoside,and daunomycin

We have investigated the effects of encapsulation within liposomes (phospholipid vesicles) on the plasma clearance kinetics and tissue disposition of four anti-tumor drugs, namely vinblastine. cytosinc arabinoside, actinomycin-d and daunomycin. In each case, subsequent to intravenous administration, the liposome-encapsulated drugs were cleared from the plasma much more slowly than were the free drugs. For example, the major portion of daunomycin injected in free form had a plasma half-life of less than 5 min, while liposome-encapsulated daunomycin had a plasma half-life in excess of 150 min. Encapsulation also caused a marked alteration in the tissue disposition of the injected drugs. Thus, encapsulation within liposomes resulted in a large increase in the total amount of drug equivalents retained by the tissues at various times after injection. In the case of cytosine arabinoside, for example, the level of drug equivalents in the liver at 16 hr post injection was 68-fold greater for liposome-encapsulated drug than for free drug. Encapsulation also altered the relative distribution of drugs in the tissues, with tissues rich in reticuloendothelial cells, such as liver and spleen, being the favored sites of uptake.     

紫杉醇脂质体在大鼠和荷瘤裸鼠体内的组织分布

目的：运用LC—MS／MS法测定紫杉醇脂质体在大鼠和荷瘤裸鼠体内的组织分布,比较注射用紫杉醇脂质体和紫杉醇注射液的体内分布特征。方法：大鼠分组后分别iv．7mg·kg-1受试和参比试剂,于给药前、给药后10min、1h、4h采集组织样品;荷瘤裸鼠分组后分别iv．10mg·kg-1受试和参比试剂,于给药前、给药后10min,1h,4h,8h采集组织样品,利用LC—Ms／Ms法对组织样品中药物含量进行测定。结果：大鼠iv．紫杉醇脂质体后10min在肝、心、肾、脑、子宫分布达到最大值．4h后各组织中药物含量均下降：荷瘤裸鼠iv．给药后10min在血、肝、脾、肺、肾、脂肪、睾丸分布量最大,8h后在脾、肠、肝、肿瘤中药物含量依然较高。结论：紫杉醇脂质体和紫杉醇注射液在大鼠和裸鼠体内的组织分布一致。静脉注射紫杉醇脂质体后．均能特异地分布到肝脏、肺和肠等。两制剂比较,紫杉醇脂质体具有更好的靶向性和更高的安全性。     

氟尿嘧啶脂质体在小鼠体内的组织分布及靶向性评价研究

目的:研究氟尿嘧啶脂质体(FU-Lip)在小鼠体内的组织分布,并评价其靶向性。方法:将90只小鼠随机均分为10组,前5组静脉注射FU-Lip,后5组静脉注射FU注射液,剂量均为25mg·kg-(1以FU计),采用高效液相色谱法测定各组小鼠血浆、心脏、肝、脾、肺、肾中24h内的FU浓度,分析药物组织分布情况,以24h内的相对摄取率(re=AUC脂质体/AUC注射液)和靶向效率(te=AUC组织/AUC血浆)判断FU-Lip对主要器官的靶向性。结果:各组织中FU浓度均先升高后降低;与FU注射液比较,静脉注射FU-Lip后24h内的平均FU浓度在肝、脾中均升高,在其他组织中的浓度均降低;FU-Lip在肝中的re为17.13,其他组织的re均≤7.017;肝、脾中FU-Lip的te1与FU注射液te2的比值分别为5.616、2.301,其他组织均≤1。结论:FU-Lip能提高药物在肝、脾中的分布,具有肝、脾靶向性,尤其是肝靶向性。     

Tissue distribution of amphotericin B lipid complex in laboratory animals.

Amphotericin B lipid complex (ABLC), under development for the treatment of serious fungal disease, is not a true liposome but a complex of amphotericin B, dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylglycerol with a particle size range of 1.6-6.0 microns. Tissue distribution of ABLC was determined in mice and rats after i.v. or i.p. administration. ABLC resembles typical liposomal preparations with amphotericin B concentrating in the reticuloendothelial system. After a single i.v. treatment with ABLC, amphotericin B was present in high concentrations in liver, lung and spleen of mice and rats while plasma levels were consistently low. Mouse liver contained 48% of the administered dose 1 h after treatment and always contained the largest amount of amphotericin B after ABLC treatment. In mice treated once daily for 7 consecutive days with 10 mg kg-1 ABLC, liver amphotericin B concentration reached 377 micrograms g-1. Tissue concentrations of amphotericin B were substantially lower when ABLC was given i.p. instead of i.v. with reticuloendothelial tissues containing 2- to 7-fold more after i.v. treatment. Animals treated with 10 mg kg-1 ABLC for 14 consecutive days showed no overt signs of toxicity and had only transient changes in liver and kidney function after treatment.     

Enhanced Tumor Targeting of Doxorubicin by Ganglioside GMl-bearing Long-circulating Liposomes

Abstract

Doxorubicin (DXR) was encapsulated in long-circulating liposomes, composed of ganglioside GM1 (GM1)/distearoylphosphatidylcholine (DSPC)/cholesterol (CH) (0.13:1:1 in molar ratio) and sized to approximately 100 nm in mean diameter, with 98% entrapping efficiency by the transmembrane pH gradient method. Free DXR, DXR-DSPC/CH and DXR-GM1/DSPC/CH liposomes were injected intravenously into Colon 26 tumor-bearing Balb/c mice via the tail vein at a dose of 5.0 mg DXR/kg. DXR-GM1/DSPC/CH liposomes gave a higher blood level of the drug than did DXR-DSPC/CH liposomes or free DXR up to 24 hours after injection, and the area under the blood concentration-time curve (AUC) for DXR-GM1/DSPC/CH liposomes was 1.5 or 526 times higher than that for DXR-DSPC/CH liposomes or free DXR, respectively. DXR-GM1/DSPC/CH liposomes gave a decreased DXR concentration in the reticuloendothelial system (RES) of the liver and the spleen. Both liposomal formulations effectively reduced the DXR concentration in the heart as compared with that in the case of free DXR. At 6 hours after i.v. injection, DXR-GM1/DSPC/CH liposomes provided an approximately 3.3- or 9-fold higher peak DXR level in the tumor as compared with DXR-DSPC/CH liposomes or the free drug, respectively. These high tumor levels of DXR appear to reflect the prolonged residence time of the liposomes. The results suggest that encapsulation of DXR in GM1-bearing long-circulating liposomes will be useful for cancer chemotherapy.     

Stavudine-loaded mannosylated liposomes: in-vitro anti-HIV-I activity, tissue distribution and pharmacokinetics

Cells of the mononuclear phagocyte system (MPS) are important hosts for human immunodeficiency virus (HIV). Lectin receptors, which act as molecular targets for sugar molecules, are found on the surface of these cells of the MPS. Stavudine-loaded mannosylated liposomal formulations were developed for targeting to HIV-infected cells. The mannose-binding protein concanavalin A was employed as model system for the determination of in-vitro ligand-binding capacity. Antiretroviral activity was determined using MT-2 cell line. Haematological changes, tissue distribution and pharmacokinetic studies of free, liposomal and mannosylated liposomal drug were performed following a bolus intravenous injection in Sprague-Dawley rats. The entrapment efficiency of mannosylated liposomes was found to be 47.2 +/- 1.57%. Protein-carbohydrate interaction has been utilized for the effective delivery of mannosylated formulations. Cellular drug uptake was maximal when mannosylated liposomes were used. MT2 cells treated continuously with uncoated liposomal formulation had p24 levels 8-12 times lower than the level of free drug solution. Further, the mannosylated liposomes have shown p24 levels that were 14-20 and 1.4-2.3 times lower than the level of free drug and uncoated liposomal formulation treatment, respectively. Similar results were observed when infected MT2 cells were treated overnight. Stavudine, either given plain or incorporated in liposomes, led to development of anaemia and leucocytopenia while mannosylated liposomes overcame these drawbacks. These systems maintained a significant level of stavudine in the liver, spleen and lungs up to 12 h and had greater systemic clearance as compared with free drug or the uncoated liposomal formulation. Mannosylated liposomes have shown potential for the site-specific and ligand-directed delivery systems with desired therapeutics and better pharmacological activity.     

Physiological pharmacokinetics and pharmacodynamics of (+/-)-verapamil in female rats

Tissue distribution and pharmacodynamics of verapamil were evaluated during steady state intravenous (i.v.) infusion and after single dose intraperitoneal (i.p.) drug administration to female Sprague-Dawley rats. In one group of rats, verapamil was infused to a steady state concentration at which time animals were killed. Verapamil-induced decreases in mean arterial pressure (MAP) were monitored during infusion and correlated with concomitantly obtained plasma verapamil concentrations. Tissue (lung, liver, renal medulla, renal cortex, cardiac muscle, skeletal muscle, perirenal fat, brain stem, cerebral cortex, and cerebellum) and plasma samples were obtained immediately after animals were killed and verapamil and norverapamil concentrations determined. Another group of rats, after receiving i.p. verapamil, were killed at 1, 3, 5, 19, and 24 h. Elimination from each tissue evaluated was described by a first order process. Elimination half-life of verapamil was similar among plasma and tissues evaluated (1.5 to 2.2 h). The per cent verapamil not bound to plasma proteins was concentration-independent and similar between rats receiving i.p. (mean +/- S.D.) (2.28 +/- 0.72 per cent) and i.v. (2.08 +/- 0.03 per cent) verapamil. MAP and verapamil concentration in plasma (r = 0.75; p less than 0.01) and cardiac muscle (r = -0.82; p less than 0.01) were inversely correlated in a highly significant fashion during both i.v. and i.p. drug administrations. The tissue-to-plasma distribution ratio for verapamil and norverapamil was similar among animals receiving i.p. verapamil at all points of sampling, suggesting distribution equilibrium had been achieved. After steady state i.v. infusion, both verapamil and norverapamil tissue: plasma concentration ratios were greater than after i.p. administration. Higher tissue: plasma verapamil concentration ratios after i.v. administration than after i.p. administration suggest either only a pseudoequilibrium is attained after i.p. administration or that determinants of tissue distribution of racemic verapamil differ with different routes of drug administration. In these studies, MAP provided a reasonable pharmacodynamic marker for verapamil tissue and plasma concentrations.     

Enhancement of Tissue Delivery and Receptor Occupancy of Methylprednisolone in Rats by a Liposomal Formulation

A liposomal formulation of methylprednisolone (L-MPL) was developed to improve localization of this immunosuppressant in lymphatic tissues. Liposomes containing MPL were formulated from a mixture of phosphatydylcholine and phosphatydylglycerol (molar ratio, 9:1) and sized by extrusion through a 0.1-µm membrane. Male Sprague–Dawley rats received a bolus dose of 2 mg/kg of L-MPL or free MPL in solution (control). Samples of blood, spleen, liver, thymus, and bone marrow were collected at intervals over a 66-hr period. Concentrations of MPL in plasma and organs and free cytosolic glucocorticoid receptors (GCR) in spleen and liver were determined. The plasma MPL profiles for free and L-MPL were bi- and triexponential. Although the alpha phase kinetics of both dosage forms were similar, L-MPL showed a substantially slower elimination phase than did free drug. Incorporation of MPL into liposomes caused the following increases: terminal half-life, from 0.48 (MPL) to 30.13 hr (L-MPL); MRT, from 0.42 to 11.95 hr, V _ss, from 2.10 to 21.87 L/kg; and AUC, from 339 to 1093 ng · hr/mL. Uptake of liposomes enhanced significantly the delivery of drug to lymphatic tissues and liver; AUC tissue:plasma ratios for spleen increased 77-fold; for liver, 9-fold; and for thymus, 27-fold. The duration of GCR occupancy was extended 10-fold in spleen and 13-fold in liver by the liposomal formulation. Lymphatic tissue selectivity and extended receptor binding of liposome-delivered MPL offer promise for enhanced immunosuppression.     

齐多夫定棕榈酸酯脂质体的制备及在小鼠体内的药物分布

目的制备齐多夫定棕榈酸酯脂质体并考察其在小鼠体内的分布情况。方法采用乙醇注入法制备齐多夫定棕榈酸酯脂质体;采用HPLC法测定静脉注射后小鼠体内齐多夫定的质量浓度。结果脂质体包封率为95.2%,粒径为(75.6±42.2)nm。小鼠尾静脉分别注射齐多夫定棕榈酸酯脂质体30.0mg.kg-1和齐多夫定溶液15.85mg.kg-1后,体内消除半衰期脂质体组为16.4min,溶液组为5.74min;30min内脂质体组肝、脾、肾和脑(15min内)中齐多夫定的AUC值分别为溶液组的1.6倍、1.19倍、80%、1.8倍。结论采用乙醇注入法制备的齐多夫定棕榈酸酯脂质体包封率高,粒径均匀;可延长药物体内消除半衰期,提高了其在肝和脑的靶向性。齐多夫定棕榈酸酯脂质体有望成为一种理想的抗艾滋病制剂,值得进一步深入研究。     

PHARMACOKINETIC EVALUATION OF LIPOSOMAL ENCAPSULATED AMPICILLIN IN MALE AND FEMALE RATS

The dispositions of free and liposomal entrapped ampicillin were compared in male and female rats after IV administration. Serial blood samples were collected for 2 h in the free drug study and 12 h for the liposomal formulation. Pharmacokinetic parameters obtained with free drug were not significantly different between genders. However, gender significantly influenced the disposition of liposomal encapsulated ampicillin. While no difference was observed in distribution t_1/2 between genders, female rats had a shorter MRT, smaller V_ss and V_t and faster clearance as compared to male rats. In a second study, spleen, liver, kidney, heart, and lung were harvested post-injection of free and liposomal entrapped ampicillin. Free ampicillin did not distribute extensively into the tissue compartment and no gender difference was noted. In contrast, liposomal encapsulation resulted in a substantial tissue uptake. In general, female rats had higher concentrations in the spleen and lung as compared to male rats. In vitro plasma stability was not significantly different, suggesting that destabilization of the liposomes does not play a large role in the dispositional differences observed in these studies. However, in vivo interaction of liposomes and plasma lipoproteins may influence the disposition of encapsulated drug. ©1997 by John Wiley & Sons, Ltd.     

Body distribution of Bothrops asper (terciopelo) snake venom myotoxin and its relationship to pathological changes

The distribution of 125I-labelled Bothrops asper myotoxin following i.m. and i.v. injections was studied in mice. After i.m. administration the toxin was concentrated in the injected gastrocnemius muscle, with relatively little binding to other tissues. Upon i.v. injection the highest radioactivity was detected in liver, kidneys, lungs, spleen and blood. A conspicuous decrease in myotoxin concentration occurred during the first hour, whereas the rate of decrease was reduced at later time periods. Only the injected skeletal muscle was clearly damaged after i.m. inoculation, as judged by histology and by the decrease in tissue creatine kinase contents. Contralateral, noninjected gastrocnemius was not affected by the toxin. Histological observations carried out after i.v. administration of the toxin revealed moderate alterations only in lungs, with a slight increase in serum levels of the enzymes creatine kinase and alanine aminotransferase.     

The kinetics and tissue distribution of protein transduction in mice.

Protein transduction domains (PTDs) offer an exciting therapeutic opportunity for the treatment of many diseases. An 11-amino acid fragment of human immunodeficiency type 1 (HIV-1) TAT-protein can transduce large, biologically active proteins into mammalian cells; recent evidence has shown an in vivo PTD for the 116 kDa beta-galactosidase protein. However, there is little information on the in vivo distribution of the TAT fusion protein to define the viability of PTDs for human studies. In this study we examined the tissue kinetics and tissue distribution of the PTD-transduced TAT fusion protein in mice. Low (100 microg) or high (500 microg) doses of TAT-beta-galactosidase fusion protein were administrated to mice through four routes (portal vein, i.v., i.p., and oral). Tissues were harvested 15 min, 1h, 6h, 10h, and 24h after treatment. Distribution of beta-galactosidase in various tissues was analysed by in situ staining, enzymatic activity assay, and Western blot analysis. Beta-galactosidase enzyme activity was observed in all tissues (liver, kidney, spleen, lung, bowel, and brain). Beta-galactosidase activity peaked at 15 min in most tissues after portal vein, i.v., and i.p. administration and at 1h after oral dosing in all tissues. Beta-galactosidase activity in the liver at 15 min after portal vein injection (67 milliunits [mU]/mg) was higher than after i.v. (9.8 mU/mg), i.p. (4.4 mU/mg), and oral (0.3 mU/mg) dosing. In situ staining and Western blot results correlated closely with beta-galactosidase enzyme activity assay. The median initial half-life for activity was 2.2h, ranging from 1.2h to 3.4h (coefficient of variation=28.9%). The bioavailability of beta-galactosidase activity after an orally administered PTD was 24%. This study details the kinetics and tissue distribution of delivering of a model TAT fusion protein into the mouse via PTD. These data allow rational selection of delivery route and schedules for therapeutic PTD and will aid the use of TAT fusion protein transduction in the development of protein therapies.     

Repeated injection of pegylated liposomal antitumour drugs induces the disappearance of the rapid distribution phase

Upon repeated administration, empty pegylated liposomes lose their long‐circulating characteristics, referred to as the accelerated blood clearance (ABC) phenomenon. To investigate whether cytotoxic drug‐containing pegylated liposomes could also elicit a similar phenomenon, two pegylated liposomal antitumour drugs (doxorubicin and mitoxantrone) were prepared, and they were administrated twice in the same animals with a 10‐day interval at a dose level of 8 mg kg^?1 (pegylated liposomal doxorubicin) and 4 mg kg^?1 (pegylated liposomal mitoxantrone). By comparing the overall pharmacokinetics after a single‐dose injection with that in animals treated with two doses, it was surprising to find that repeated administration of pegylated liposomal antitumour drugs caused the disappearance of rapid distribution phase instead of the ABC phenomenon, resulting in the conversion of a two‐compartment model to a one‐compartment model. Further investigation revealed that repeated injection induced the decreased uptake of liposomal antitumour drugs by the spleen at the early time point of 0.5–8 h after injection. In contrast, the deposition of liposomal antitumour drugs into liver was not affected. Therefore, the disappearance of the rapid distribution phase might be related to the reduced spleen uptake at the early time point.     

Increase of thiopental concentration in rat tissues due to anesthesia with isoflurane.

Thiopental distribution was studied in rats (30 mg/kg i.v.) anesthetized simultaneously with 1.25 "rat"-MAC isoflurane. The thiopental concentration in serum and several tissues was determined UV-photometrically at 305 nm after extraction and TLC. In the serum of rats anesthetized with isoflurane the thiopental concentration was significantly increased to +39----+74% in comparison to controls during 30 min following the barbiturate injection. Also in liver, brain, heart, kidney, lung and spleen of rats anesthetized with isoflurane the thiopental concentration was significantly increased at 3 and 10 min; at 30 min the difference vs. control had vanished in brain, heart, lung and spleen. Obviously, thiopental was transiently "trapped" during the early distribution phase to a considerable amount in these vessel-rich tissues when anesthesia with isoflurane was simultaneously performed; this pharmacokinetic interaction might be explained at least to some extent hemodynamically; in many tissues regional blood flow is reduced during anesthesia with isoflurane; thereby the "washout" of thiopental from the tissues and the redistribution are delayed.     

异长春花碱脂质体的制备及其在小鼠体内的组织分布

目的:制备异长春花碱(VRB)脂质体并考察其在小鼠体内的组织分布情况。方法:采用薄膜分散法制备VRB脂质体;以Lewis肺癌C57BL/6J荷瘤小鼠为模型,分为对照组(VRB注射液)和脂质体组(VRB脂质体),每组24只,分别尾静脉注射10mg·kg-1,于给药后0.5、2.0、12.0h取样,以高效液相色谱法测定各组小鼠不同时间血浆、心、肝、脾、肺、肾、肌肉、大脑、肿瘤中的药物浓度,并计算制剂的靶向性参数。结果:制备的VRB脂质体的平均粒径为158.3nm,脂质体外观圆整、大小均匀,可见明显的双分子层结构;与VRB注射液比较,VRB脂质体在模型小鼠肝、脾、肿瘤中3个时间点的分布均明显增强(P<0.05或P<0.01),其余组织分布无明显变化;VRB脂质体对模型小鼠具有明显的肝、脾、肿瘤靶向性及一定的肺靶向性。结论:所制备的VRB脂质体对肺癌模型小鼠肿瘤组织具有明显靶向性。